In the treatment of pulp suspensions there is a need for intermixture of different media for treatment, for example for heating or bleaching purposes. Therefore it is desirable to disperse the medium in the pulp suspension during simultaneous conveyance of the pulp suspension through a pipe. European Patent No. 664,150 discloses apparatus for this function. For heating of pulp suspensions, steam is added which condenses and thus gives off its energy content to the pulp suspension. A bleaching agent is added during bleaching that reacts with the pulp suspension. In connection with the treatment of recovered fiber pulp printing ink is separated by flotation, which means that air must previously be disintegrated in the pulp suspension such that the hydrophobic ink, or the printing ink, may attach to the rising air bubbles. In this connection it is desirable that the medium for treatment, e.g. air, is evenly and homogeneously distributed in the pulp suspension, preferably with tiny bubbles to achieve a large surface against the pulp suspension.
In all cases it is difficult, with proportionately low addition of energy, to achieve an even intermixture of the medium in the flow of material. When heating pulp suspensions by the supply of steam to a pulp pipe, problems often arise with large steam bubbles that are formed on the inside of the pipe, and this as a consequence of a non-disintegrated gas with a small condensation surface. When these large steam bubbles rapidly implode, condensation forces arise that cause vibrations in the pipe, and in the following equipment. This phenomenon limits the amount of steam that can be added to the system and thus the desired increase in temperature. It is hard to achieve a totally even temperature profile in the pulp suspension when large steam bubbles exist. In order to remedy these problems, a large amount of energy can be supplied to carefully admix the steam in the pulp suspension. Another variant is to disintegrate the steam already supplied with the pulp suspension. In the intermixing of bleaching agents in a pulp suspension, relatively large amounts of energy are used in order to provide that the bleaching agent is evenly distributed and conveyed to all the fibers in the pulp suspension. The energy requirements are controlled by which bleaching agent is be supplied (rate of diffusion and reaction velocity) and also by the phase of the bleaching medium (liquid or gas). The geometry during supply of the bleaching agent in vapour phase is important in order to avoid unwanted separation immediately after the intermixture.
One object of the present invention is to provide an apparatus for supplying and intermixing of a chemical medium in a pulp suspension in an effective way and that at least partly eliminates the above mentioned problem.